Copolymer concentrate and
oil composition



United States Patent 3,210,282 COPOLYMER CONCENTRATE AND OIL COMPOSITIONCharles R. Bearden, Lake Jackson, Tex., assignor to The Dow ChemicalCompany, Midland, Mich., a corporation of Delaware No Drawing. FiledOct. 25, 1961, Ser. No. 147,489 2 Claims. (Cl. 25251.5)

This invention relates to copolymers useful in improving lubricatingoils and to lubricating oils containing such copolymers.

The principal use for lubricating oils is in internal combustionengines, the efliciency of which depends to a large degree upon thequality of the crankcase oils employed. A major problem in the operationof internal combustion engines, which may be broadly classified as sparkignition and diesel types, results from the tendency of conventionalcrankcase oils to undergo oxidation and other chemical changes that leadto the formation of carbon, resins, and insoluble varnish-like gumswhich deposit on moving engine parts and separate as sludge thatmarkedly impairs the lubricating properties of the oil. Another sourceof sludge is the decomposition of the fuel and this source isparticularly damaging since the deposits occur on piston surfaces andaround piston rings. Sludge formation and gum deposition are most severein light duty engine operation as exemplified by intermittent use ofpassenger automobiles and light trucks.

Many materials have been added to lubricating oils to improve them andconsiderable knowledge of such adjuvants has been gained. Some of thespecific additives used to improve the properties of lubricating oilsare pour point depressants, the viscosity index improvers (VIimprovers), and the sludge dispersants and detergents. Lubricating oilshave thus been formulated to improve performance with respect to one ofthese properties, i.e., improved viscosity index or better sludgedispersing or detergent action, and in some cases, lubricating oiladditives have been prepared which, when blended with a lubricating oil,provide improvement with respect to two of these properties. Forexample, certain high molecular weight polymethacrylic copolymers areuseful as both pourpoint depressants and VI-improvers. Other copolymers,such as those prepared from alkyl methacrylates withN-vinyl-alkyl-oxazolidinone or N-vinylpyrrolidinone are of similarutility. However, among the known lubricating oil additives, there isnot one that will improve all the properties of a lubricating oilequally at the same time. No detergent or sludge-dispersant additive forlubricating oils has heretofore been proposed that provides more than apartial answer to the problem of preventing sludge formation and varnishdeposition in engines. In fact, known oil detergents in many casesincrease the rate of accumulation of inorganic deposits within thecombustion chambers of engines.

It is an object of the present invention to provide a copolymer suitablefor mixing with lubricating oils.

Another object is to provide a copolymer which, when added to alubricating oil, greatly improves the dispersant and detergentproperties, improves the VI, reduces the pour point, and inducesprolonged resistance to sludge and varnish formation. Other objects willappear hereinafter.

It is understood that the term lubricating oil, as used herein, is to beinterpreted broadly as referring to natural and synthetic lubricatingoils. These oils are essentially hydrocarbons which possess lubricatingproperties regardless of their actual viscosity and include crude orrefined petroleums, hydrogenated petroleum oils, or hydrogenated crackedpetroleum oils, oily high molecular 3,210,282 PatentedOct. 5, 1965 iceweight hydrocarbons, such as are obtained by the polymerization ofolefins or by the condensation of olefins with aromatic hydrocarbons,etc.

One or more of the above objects are accomplished according to thepresent invention by copolymerizing at least one alkyl acrylate, oralkyl methacrylate with N-vinyl- 3-morpholinone (hereinafter designatedVM). While a wide latitude is permissible in choosing the arcylic esterand the proportions thereof in the copolymer, it is essential (1) thatthe copolymer be oil-soluble, (2) that it contain at least one acrylicester containing an alkyl radical of at least about 12 carbon atoms, and(3) that it contain sufficient VM to improve its sludge-dispersantproperties. To meet the first requirement, it is preferred that theacrylic ester (i.e., the alkyl acrylate or mathacrylate) componentconsist predominantly of ester or esters wherein the alkyl radical orradicals contain at least 4, and preferably at least 6 carbon atoms. Tomeet the second requirement, at least about 20 percent, and preferablyabout 50-80 percent, of the acrylic ester component should contain analkyl radical of at least 12 carbon atoms. Obviously, the firstrequirement will often inherently be met in fulfilling the second. Thethird requirement may be met by the inclusion in the copolymer of only avery small proportion of VM. As little as 3 percent usually produces avery evident improvement in the product, though it is generallynecessary to use at least 5 percent or even 10 percent, to achieveoptimum results. On the other hand, amounts in excess of about 20percent are usually uneconomical and over about 30 percent produceslittle, if any, added improvement. Thus, the preferred copolymerscontain about 3-30 percent of VM, the optimum usually being about 10-20percent.

In view of the above considerations, the acrylic ester component of thecopolymer of the invention ordinarily consists of one or more estershaving the formula wherein n is an integer from O to 1 and R is an alkylradical containing about 4 to 20 carbon atoms. Best results are obtainedwhen R is a straight-chain primary alkyl radical. In a preferredembodiment, the acrylic ester component of the copolymer comprises atleast one ester wherein R contains 4 to 8 carbon atoms and at least oneester wherein R contains 12-20 carbon atoms.

The copolymers of the invention are preferably prepared by dissolvingone or more of the acrylates or meth acrylates and VM in a diluent oiland copolymerizing at elevated temperatures under an oxygen-freeatmosphere in the presence of a free-radical-producing compound whichacts as a catalyst or initiator. Polymerization may also be induced byirradiation under the influence of high energy fields. The lattercatalyzation may include the various actinic radiations, including suchdiverse forms of catalysis as ultraviolet, X-ray and gamma radiations,as well as radiation from radioactive mate rials and high energyelectrons generated from linear accelerators, resonant transformers andthe like.

Elevated temperatures are preferred during the course of thereaction inorder to decrease the reaction time. Preferably, the temperature rangeis about 40 to about C., but temperatures either higher or lower may beemployed depending upon the catalyst.

The diluent oil is preferably a conventional low sulfurcontent oil, suchas the parafiinic hydrocarbon or ester type, which is suitable foraddition to lubricating oils.

The monomers are suitably employed in such proportions that the diluentwherein they are copolymerized will contain, after polymerization, fromabout 15 percent to about 60 percent, and preferably about 25 percent to40 percent of copolymer. All percentages specified herein are by weight.And while copolymerization directly in a diluent oil of the type statedis the preferred method, other methods may be employed, as for example,polymerizing the monomers in the lubricating oil in which the copolymeris to be used or in an inert volatile hydrocarbon diluent such as hexaneor toluene. However, alternate methods such as these are generally lessdesirable. For example, when a volatile solvent is employed in place ofa diluent oil, it must be removed, e'.g., by distillation, after thepolymerization, and replaced with oil.

When the polymerization is brought about in a diluent oil, the oilcontaining the copolymer may be considered as a concentrate containingthe copolymer in the aforesaid amount. The concentrate suitably isincorporated into a lubricating oil to the extent that the copolymerwill be in an amount in the range of from about 0.1 percent to about 20percent and preferably from 3 percent to 8 percent of the lubricatingoil.

The following examples illustrate the practice of the present invention.

EXAMPLE 1 Into a reaction vessel equipped with a means for stirring,purging, and temperature control were placed 200 ml. of white mineraloil (180 SUS, Saybolt Universal seconds), 50 ml. of hexyl meth-acrylate,60 ml. of lauryl methacrylate, 60 ml. of stearyl methacrylate, 30 ml. ofVM and 1 gram of lauryl peroxide. The mixture was maintained at atemperature in the range of from 60 to 80 C. for 18 hours while under anitrogen atmosphere. At the end of 18 hours, a concentrate of 50 percentcopolymer in white mineral oil was obtained.

EXAMPLE 2 Into a reaction vessel equipped with a means for stirring,purging, and temperature control were placed 20.8 pounds of 180 SUSwhite mineral oil, 2.12 pounds of VM, 3.54 pounds of hexyl methacrylate,5.1 pounds of lauryl methacrylate, 3.4 pounds of stearyl methacrylate,and 95 g. of lauryl peroxide. The mixture was maintained at atemperature of 63 C. for 15 hours while under a nitrogen atmosphere. Atthe end of 15 hours a concentrate of 40 percent copolymer in whitemineral oil was obtained.

This composition was blended and tested in an engine according to theCo-ordinating Research Council (C.R.C.) FL-Z technique. The blend wasmade by rnixing 1.5 pounds of the above concentrate with 30 pounds of150 SUS solvent-refined neutral petroleum oil. This produced a petroleumoil containing 2 percent of copolymer. In addition, 0.8 percent of zincdialkyl dithiophosphate was added as an oxidation inhibitor. The blendhad the following properties and give the following results:

Blend Base Oil SUS 210 F. viscosity 10. 1 6.0 100 F. Viscosity. 60. 439. 0 i i t 58 it 0111 OlIl Sludge rating. 68.4 out of possible so.Varnish rating 15.0 out of possible 20.

4 EXAMPLE 3 Into a reaction vessel equipped with a means for stirring,purging and temperature control were placed 210 g. of white mineral oil,9 g. of VM, 27 g. of hexyl methacrylate, 33 -g. of lauryl rnethacrylate,21 g. of stearyl methacrylate, and 1 g. of lauryl peroxide. The mixturewas maintained at a temperature of 65 C. for 18 hours while under anitrogen atmosphere. At the end of 18 hours a concentrate of 30 percentcopolymer in white mineral oil was obtained.

This composition was blended and tested in an engine according to theC.R.C. FL-Z techinque. The blend was prepared by mixing a sufficientamount of the 30 percent copolymer into SUS solvent refined neutralpteroleum oil to produce a 2 percent mixture and in addition, /2 percentof a 50 percent oil blend of zinc diamyl dithiocarbamate, /2 percent ofan octylated and styrenated diphenylamine, /2 percent of a zinc dialkyldithiophosphate, and 0.4 percent of a calcium-organic compoundcontaining combined sulfur, were added as oxidation inhibi- EXAMPLE 4 Acarbon dispersion test was performed to evaluate the copolymers withregard to their efiiciency in im proving lubricating oils. A paste wasprepared by thoroughly blending 20 percent of carbon black into whitemineral oil. For the test, 3 g. of this paste were blended with 70 ml.of kerosene containing 1.5 percent of the compound to be tested. Theresults are given in Table 1 and it is pointed out that the longer thedispersion stands without settling, the better is the additive. Also, inTable 1, there is a column labeled wet. Since moisture accumulates in acrankcase and is destructive with regard to the etiicieny of theadditive, this column shows the result obtained when 0.3 ml. of waterwas added to the suspension.

A hexane-insolubles suspension test was performed to further evaluatethe polymer with regard to its efiiciency in improving lubricating oils.For this test, hexane-insoluble material was obtained from oil oxidizedin a Doornte type oxidation machine and these insolubles were washedwith hexane, dried and dissolved in benzene in an amount suflicient toform a solution of 2.5 g. per liter. In order to test the ability of theadditives to suspend sludge, it was necessary to precipitate theoxidized oil insolubles in the presence of the additives. This wasaccomplished by mixing 20 ml. of the benzene solution with 10 ml. of akerosene solution containing 6 1.5 percent copolymer and heating withstirring. Reinitiator, at a temperature of about 4090 C. and for movalof the benzene was effected in 30 to 40 minutes. a time sufiicient toeffect substantially complete polym- Vials of this suspension were thenobserved and the reerization of said monomers. sults obtained are shownin Table 2. 2. A lubricating oil as defined in claim 1, wherein Table 25 the proportion of copolymer is 0.1 to 20 percent.

Product: Observation References Cited by the Examiner (1) 1.5 percent ofcopolymer Cleansolution; no UNITED STATES PATENTS of Example 1 sediment.percent of barium Cloudy Solution; Lorensen et al sulfonate Sediment2,892,788 6/59 Stewart et a1. 25251.5 (3) 1.5 percent of calicum Cloudysolution; 2949445 8/60 Blake mac-861 sulfonate sediment 2,980,658 4/61Ham 26086.1 4 percent f a copoylmel- 2,987,509 6/61 B rgert like No. 5of Table 1 Heavy sediment. 15 31003845 10/61 Ehlers 26O861 X 3,052,6489/62 Bauer 252--51.5 X I claim: 1. A hydrocarbon lubricating oil havingdissolved FOREIGN PATENTS therein, in an amount to improve the viscosityindex thereof, a copolymer of (a) 3 to 30 percent ofN-vinyl-3-m0rpho1inone and (b) at least one acrylic ester having theformula OH2=(IJ-C o o R OTHER REFERENCES DH A New Class of PolymericDispersants for Hydrowherein n is an integer from 0 to 1 and R is analkyl Carbon y Du Pont de Nemoufs & P p radical i i 4 to 20 carbonatoms, at 1 m 20 presented before th Meeting of American Chemicalpercent of said copolymer consisting of an acrylic ester y, April 1,1954, Pagfis as defined above wherein R contains at least 12 carbon Iatoms, said copolymer being made by the copOlymeriza- DANIEL WYMANpnmm'y Exammertion of the appropriate monomers under an oxygen-free 30JULIUS GREENWALD, Examiner atmosphere, in the presence of afree-radical-producing 216,911 7/58 Austraila. 226,954 2/60 Australia.808,665 2/ 59 Great Britain.

1. A HYDROCARBON LUBRICATING OIL HAVING DISSOLVED THEREIN, IN AN AMOUNTTO IMPROVE THE VISCOSITY INDEX THEREOF, A COPOLYMER OF (A) 3 TO 30PERCENT OF N-VINYL-3-MORPHOLINONE AND (B) AT LEAST ONE ACRYLIC ESTERHAVING THE FORMULA